4- FLOEA OF ATISTBALIA. 



they do not correspond in the length of the operculum. The 

 same also may be said of the species called mahogany, one of- 

 which must be referred to each division of the genus under the 

 present arrangement, whereas common sense would lead us to 

 keep them in the same group. Dr. I\ Mueller has suggested a 

 new division of the species which he denominates " the Cortical 

 System," because it is founded upon the difference of the barks, 

 and he proposes to divide all the species into the following groups : 

 (1) LeiophloicR, or those having the bark smooth all over : (2) 

 HemipTiloice, which have the bark partially persistent, but never 

 on the branches ; (3) Mhytipliloice, with the bark persistent on 

 the branches and stems, and rather solid ; (4) Schizophloice, with 

 the bark persistent and deeply furrowed ; (5) Pachyphloice, with 

 the bark fibrous and persistent ; and (6) LepidopJiloios with the 

 bark quite lamellar, resembling mica schist. Much might be said 

 in favour of this arrangement, as it is one which commends itself 

 even to the casual observer : and if in connexion with it, due at- 

 tention were paid to the shape of the seed vessel, it seems highly 

 probable that many of the anomalies of the present system would 

 be obviated. In some of the species described even in standard 

 works, the seed vessels are scarcely noticed, and the descriptions 

 are, in other respects, so defective and unsatisfactory, that it is 

 almost impossible to ascertain the exact species indicated. The 

 seed vessels are generally turbinate, hemispherical, or approaching 

 campanulate ; and hence, when taken in connexion with the 

 cortical system, they offer a good mark of distinction for classifi- 

 cation. There is reason to believe that in some instances, an un- 

 necessary multiplication of species has occurred from placing too 

 much reliance on apparent specific differences in dried specimens, 

 without an examination of that which differs the least in the same 

 species, viz., the shape and divisions of the seed vessel. In this 

 genus little reliance can be placed on the size and shape of the 

 leaves, for in some species they may be found of various forms on 

 the same tree. Beyond indeed indicating the prevalent shape, 

 texture, and veining of the leaves, it seems almost useless to dwell 

 on matters which afford no certain guide for the distinction of 

 species. The common grey gum or hybrid box is a remarkable 

 instance of the variation to which leaves in the same species are 

 subject, for on it they may be found of all shapes from narrow 

 lanceolate to broad ovate. 



